The Reaction of Protonated Dimethyl Ether with Dimethyl Ether: Temperature and Isotope Effects on the Methyl Cation Transfer Reaction Forming Trimethyloxonium Cation and Methanol
Bibliographic record
Abstract
Fourier transform ion cyclotron resonance mass spectrometry has been used to study the temperature and deuterium isotope effects on the methyl cation transfer reaction between protonated dimethyl ether and dimethyl ether to produce trimethyloxonium cation and methanol. From the temperature dependence of this bimolecular reaction it was possible to obtain thermodynamic information concerning the energy barrier for methyl cation transfer for the first time. From the slope of an Arrhenius plot, a value for DeltaH(++) of -1.1 +/- 1.2 kJ mol(-1) was obtained, while from the intercept a value for DeltaS(++) of -116 +/- 15 J K(-1) mol(-1) was derived. This yields a DeltaG(++)(298) value of 33.7 +/- 2.1 kJ mol(-1). All thermodynamic values were in good agreement with ab initio calculations. Rate constant ratios for the unimolecular dissociation forming trimethyloxonium cation and the dissociation re-forming reactants were extracted from the apparent bimolecular rate constant. Attempts at modeling the temperature dependence and isotope effects of the unimolecular dissociation forming trimethyloxonium cation were also made.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".